Materials You Cannot Compost
Composting isn't a free-for-all. You can't toss in anything and everything you come across waste-wise and expect it to produce usable, healthy compost. Some materials definitely don't qualify as compost ingredients because they contain pathogens, attract pests, or cause other problems. Save yourself hassles and headaches by keeping the following items out of your composting operation:
Meat, bones, grease, fats, oils, and dairy products: They turn rancid and smelly and attract dogs, cats, raccoons, foxes, and rodents.
Feces: Waste from dogs, cats (including soiled cat litter), pet birds, pigs, and humans may contain parasites that are transferable to and infectious for humans.
Charcoal barbecue or coal ashes: All gardeners should leave these alone because they contain sulfur oxides and other chemicals you don't want to transfer to your garden.
Wood ashes: Wood ashes are alkaline. If you garden where soils are alkaline (like much of the western and southwestern United States) you don't want to increase alkalinity by adding ashes to your compost mix. However, if you garden where soils are acidic, wood ashes can be added in small amounts. Sprinkle handfuls throughout as you mix a pile.
Treated wood products: Don't add wood chips or sawdust from chemically treated or pressure-treated wood.
If you become a serious composting enthusiast who likes to monitor and maintain hot piles, the following three items can be composted. Monitoring your pile's temperature and turning it frequently are essential. If you describe yourself as a laid-back, "compost happens" gardening guy or gal, you're better off safe than sorry. Dispose of these problem-prone plant materials in the trash:
Weeds with seed heads. You can pull weeds before they go to seed and toss them in your compost pile as a good source of nitrogen. But if seeds have set, toss the entire plant in the trash.
Disease- or insect-infested plant material.
Plants that spread with invasive root systems, such as African couch grass, Bermuda grass, bindweed, Canada thistle and other thistles, dock weed, morning glory, and nettle. Just a smidgen of this root material can survive to sprout another day and spread havoc throughout your garden.
If throwing away organic matter, no matter how weedy and disease-ridden, sends minor guilt pangs up and down your spine but you don't have time to regularly maintain a hot pile, stockpile all the bad stuff in a separate bin where it can't inadvertently be mixed in with the good stuff. Or place all the bad stuff in a large (30- to 40-gallon), black, thick plastic garbage bag and seal it. When the quantity is sufficient and you have plenty of green, nitrogen-rich materials (such as grass clippings or manure) to add to it, build one pile to neutralize the problems. Laboring over just one hot heap per garden season isn't as time-consuming as ensuring that every pile heats up to the red zone.
Another option is to take diseased or invasive plant material to your local recycling center that collects green waste. Ask if they compost at sufficiently high temperatures to destroy your problem plants. If they do, make your contribution; if they don't, it's back to Plan A.
Gardening Glossary
annuals
Plants that complete their entire life cycle within one growing season. The plant germinates from seed, grows and blooms, and then produces seed and dies.
Gardening Glossary
biennials
A plant that take two growing seasons to complete its life cycle. It germinates and grows leaves and stems in the first year; produces flowers and fruit (seed) in the second, and then dies.
Gardening Glossary
bolt
When a plant flowers or produces seed prematurely.
Gardening Glossary
cold frame
A wooden or concrete block box in which you can grow plants or hold dormant during the cold winter months.
Gardening Glossary
cole crops
A family of vegetables, including broccoli, cabbage, cauliflower, kale, and Brussels sprouts. They thrive in cooler weather.
Gardening Glossary
complete fertilizer
Any fertilizer that contains all three of the primary nutrients, N-P-K (nitrogen, phosphorus, potassium). Phrase is based on regulations governing the fertilizer industry. Does not mean that the fertilizer literally contains everything a plant needs to thrive.
Gardening Glossary
deadheading
The practice of pinching or cutting off spent flowers
Gardening Glossary
evaporative-pad humidifier
A humidifier in which fans blow across a moisture-laden pad that sits in a reservoir of water.
Gardening Glossary
harden off
The process of acclimating plants grown indoors gradually to the brighter light and cooler temperatures of the outside world.
Gardening Glossary
hardiness
The ability of a plant to survive is called its hardiness.
Gardening Glossary
humus
A stable end product of organic-matter decomposition that's believed to increase microbial activity in soil, improve soil structure, and enhance the root development of plants.
Gardening Glossary
Bacillus thuringiensis Bt
An effective bacteria that attacks only the larvae of caterpillar family insects. It is safe to other insects, animals, and humans.
Gardening Glossary
macronutrients
Mineral nutrients that plants need in the largest quantities: nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
Gardening Glossary
mulch
Organic or inorganic material placed over the surface of soil, usually directly over the root zone of growing plants. Used to conserve moisture, kill weed seedlings, modify soil temperature, provide attractive covering to garden beds.
Gardening Glossary
organic matter
Once-living stuff like compost, sawdust, animal manure, ground bark, grass clippings, and leaf mold (composted tree leaves). Used to enrich soil and improve soil texture.
Gardening Glossary
perennials
Any plant with a life cycle of three or more years. Herbaceous (non-woody) perennials include flowering plants and herbs, mainly. Woody perennials include trees and shrubs. Longevity depends on the plant and growing conditions.
Gardening Glossary
pH
The measure of soil's acidity. Soil with low pH means it's too acidic; soil with high pH means it's alkaline. Most plants grow best in soil with a pH value between 6.5 and 7.2. Neutral soils measure 7.
Gardening Glossary
photosynthesis
The process through which plants take nutrients from the air and from the water in the soil to produce sugars that fuels the plant's growth.
Gardening Glossary
primary nutrients
Nitrogen, phosphorous, and potassium are the three nutrients plants need in the largest quantities.
Gardening Glossary
root crops
Plants with edible underground roots such as onions, carrots, beets, potatoes, turnips. Most root crops are cold-weather crops.
Gardening Glossary
self-blanching
A type of cauliflower with leaves that naturally curl over the head and exclude light. Requires cool temperatures for leaves to curl effectively.
Gardening Glossary
sets
Small onion bulbs, about 1/2-inch wide, that were started from seed the previous year. Grow onion sets with the pointy end up.
Gardening Glossary
side-dressing
The act of adding a small amount of fertilizer around or "on the side" of plants after they're growing.
Gardening Glossary
succession planting
Planting small, 2-to-4-foot patches of plants every two weeks throughout the growing season so that you can harvest a crop over an extended period of time.
Gardening Glossary
thinning
The act of cutting the least robust seedlings in your garden to give the healthier plants more room to grow.
Gardening Glossary
vining crops
Crops that grow on vines, such as cucumbers, melons, pumpkins, and winter squash. They usually require support (staking, trellising, etc.) to keep them off the ground.
